November 6, 2012

Scientists Develop New Method To Visualize Fingerprints

Fingerprint evidence is often used in court cases to finger the guilty party. Sad puns aside, while using fingerprints can be a reliable way to identify a subject, it´s not always easy to find a clear and usable print. Now, a team of scientists at the Hebrew University of Jerusalem have created a new method to visualize these fingerprints by creating a negative image, making them much easier to read and much more accurate.

This team of Hebrew scientists were led by Prof. Yossi Almog and Prof. Daniel Mandler of the Institute of Chemistry at the Hebrew University. In order to develop the easy-to-read prints, the team use a chemical process which creates a negative image of the prints, similar to the way a black and white picture is developed. The team will have their new process explained in the latest issue of the journal Angewandte Chemie, which is published by the German Chemical Society.

Paper evidence is used in many criminal investigations and the fingerprints planted within can be helpful to determine who handled important documents, such as checks, currency, etc. However, the method used to pull these fingerprints off of these pieces of paper isn´t always accurate or very visible. This is due to the process used to find these fingerprints. Our hands have sweat and oil glands which are responsible for leaving fingerprints. As our hands touch things, such as pieces of paper (which are already prone to absorbing oil and sweat) our fingerprints are left behind. The prints are shown in a positive layout, with the oil and sweat leaving behind the indentations of our rings on whatever it is we´ve touched.

In the conventional method, these prints are found by using gold particles which stick to the areas of sweat. Then, silver particles are placed on top of the gold to make the prints more visible. This method creates an image of the prints which can sometimes be hard to read. Some studies have even showed that less than half of the fingerprints developed in this way can be used to accurately link a person with the fingerprints.

The new method also uses the main elements of gold and silver, oil and sweat, but uses them in a different and innovative way to produce a clearer, more accurate print.

Instead of sticking to the sweat, the gold particles used in the new method stick to the paper. The oil secreted by our oil glands helps to keep the gold from interfering with the paper and the print, acting as a sort of buffer between the two. Then silver is used to turn the areas with gold on them to black, creating an easy-to-read, negative image of the print.

“Since our method relies only on the fatty components in the fingerprints, the sweaty aspects play no role in the imaging process,” explains professor Almog. This new procedure can even be used if the piece of paper in question has become wet.

“If paper has become wet, it has previously been difficult to detect fingerprints because the amino acids in the sweat, which are the primary substrate for current chemical enhancement reactions, are dissolved and washed away by water, whereas the fatty components are barely affected.”

By not depending on the presence of sweat, police labs will be able to find prints on even more items, says professor Almog. This, he says, could lead to more accurate prints as well as more accurate results from criminal investigations.